The present invention relates to the method of producing roughened and oxidized well chips and the well chips themselves. One use for the chip of this invention is in the field of functional genomics for DNA testing wherein the chip would hold or carry multiple, such as 24, 96 or 384, DNA samples.
As the biotech industry continues to integrate applicable semiconductor processes into both existing and new product designs, the unique application for xe2x80x9cchipsxe2x80x9d with wells to hold or carry DNA samples has required the development of a unique process to form chips with 125 xcexcm and 400 xcexcm deep wells, roughened and oxidized, typically with a uniform blue thickness.
Chemical etching of silicon (2.0 xcexcm+technology) has been a standard practice in wafer processing for many years, but typical depths were only several microns deep with current technologies engaging plasma methods. The typical potassium hydroxide silicon wet etched process requires the deposit of a nitride protective film and then the removal of that nitride in the well area via a single wafer etch technique using SF6 gas followed by removal of the photo-resist in solvent such as NMP at 90xc2x0 C. for 10 minutes and then rinsed and dried. Then the wafers are placed in a heated (70xc2x0 C.) KOH bath. For 125 xcexcm deep wells, five hours can be required and for 400 xcexcm deep wells, sixteen hours can be required to etch the wells. Two heated KOH baths are required to compensate for depletion of the etchant. Then to remove the remaining nitride and roughen the well bottoms in parallel the wafers are placed in a Branson IPC using SF6 gas @ 100 watts for one hour.
The microabrasion process of the present invention produces the roughened wells easier, simpler, cheaper and more reliably.
A beadblasting process with the present invention not only offers an optimum roughing process but can form 400 xcexcm deep wells by using a mask to protect the non-well area. This enables the wells to be formed and roughened, while being protected with a cost-effective disposable mask. In addition, since the majority of the wafer is not exposed to the microabrasion process, only the desired well area is roughened, enabling the growth of a uniform oxide color thereafter, advantageous in functional genomics.